As we know that the guitar string will vibrate about its mean position in such a way that it will oscillate to and fro.
Due to this to and fro motion of the string of the guitar the air molecules will start oscillating and this disturbance of air will produce sound in the air column attached with the guitar string
So here the motion of guitar string is to and fro motion about the mean position of the string
this type of to and fro motion about the mean position is known as Vibrational Motion.
